“Dear God in heaven, even these people can’t be that mad!”

The Wicker Man is widely regarded as one of the best horror films ever made, and is regularly trotted out in the top 10 of every film critic's list of influential movies. Not bad for a bloodless musical thriller-cum-travelogue through the Western Isles which was disowned by its makers on release.

Police officer Sgt Howie (Edward Woodward) is on a quest for a missing girl, Rowan Morrison. But on the island of Summerisle where she supposedly lives, no-one has heard of her - not even the woman who is supposed to be her mother.

That evening Howie walks into the local pub, where, in the best tradition of Hammer horror, everything goes silent. However, it doesn't take long for the lusty locals to break into a chorus of song "The Landlord's Daughter" on the entrance of Britt Ekland (Willow, the landlord's daughter).

After a "disgusting" meal, Howie makes his way back outside, where he finds lots of couples enjoying the evening air in the nearby graveyard - not to mention someone watering a grave and a naked woman crying on a gravestone. Back in the pub, he goes to bed and Willow starts some naked wall-banging shenanigans, making Howie go all sweaty - but he steadfastly refuses to relent to her singing.

"I thought you were gonna come and see me last night," says Willow, the next morning. "I invited you."

But Howie explains he doesn't believe in "it" before marriage.

After finding out that paganism is taught at the local school ("everywhere I go on this island I see there's degeneracy"), Howie finds that Rowan's name IS in the school register, rather suggesting that she does exist, after all: "You're liars - you are despicable little liars!"

Much like the beetle he sees being tortured by the schoolchildren at the school ("Little old beetle goes round and round," says a girl. "Poor old thing."), Howie is getting more and more frantic.

He travels to the island’s castle to meet their Lord (Christopher Lee). Lord Summerisle’s home has some interesting garden decorations that haven’t really caught on in the intervening years - phallic hedges and hot and cold running naked girls.

"I trust the sight of the young people refreshes you?" asks Summerisle. "They are naked." replies Howie.

"Naturally, it's much too dangerous to jump through fires with your clothes on," comes the reply.

In his discussions with the Lord, it's Howie who comes across as the zealot. On God, Summerisle explains: "He had his chance - and, in modern parlance - he blew it."

After discovering that Rowan's grave is empty (another Hammerish scene - a night time exhumation) and that this year's harvest failed, Howie leaps to the conclusion that the islanders plans to sacrifice the young girl in order to appease their gods. After reading up on the May Day celebrations (and getting all the clues as to what's actually going on, but not realising it), Howie rushes towards his appointment.

It isn’t until the last few minutes, when Rowan finally appears, that everything falls into place. And it doesn't matter how many times you see it, or whether you know exactly what to expect (and everyone does) - the look on Howie's face when he realises what the smiling, dancing islanders have in store for him and his useless screams for mercy and absolution are truly terrifying - and something which stay with you long after the Wicker Man has bowed his head to the setting sun.